Quaternary ammonium salts of methenamine

ABSTRACT

QUATERNARY AMMONIUM SALTS OF THE FORMULA   (2-R,4-(NO2-)PHENYL)-CH2-(N(-CH3))3-N(+)(-CH3)3 X(-)   WHEREIN R IS HYDROXY OR LOWER ALKOXY, AND X- IS THE ANION OF A PHYSIOLOGICALLY TOLERATED ACID AT LEAST AS STRONG AS PHOSPHORIC ACID HAVE BEEN FOUND TO HAVE ANTIMICROBIAL EFFECTS ON MANY TYPES OF PATHOGENIC MICROORGANISMS WHICH CAUSE INFECTIONS OF THE INTESTINAL AND URINARY TRACT.

United States Patent Office 3,574,209 Patented Apr. 6, 1971 3,574,209 QUATERNARY AMMONIUM SALTS F METHENAMINE Hans Suter, Dorflingen, and Hans Zutter, Schalfhausen,

Switzerland, assignors to Schweizerisches Serumund Impfinstitut und Institut zur Erforschung von Infektionskrankheiten, Bern, Switzerland No Drawing. Filed May 26, 1969, Ser. No. 827,950 Claims priority, applicatgirfir l1 1S/vgitzerland, June 27, 1968,

Int. cl. C07d 55/52 US. Cl. 260-4485 3 Claims ABSTRACT 0F THE DISCLOSURE Quaternary ammonium salts of the formula wherein R is hydroxy or lower alkoxy, and X- is the anion of a physiologically tolerated acid at least as strong as phosphoric acid have been found to have antimicrobial effects on many types of pathogenic microorganisms which cause infections of the intestinal and urinary tract.

This invention relates to compounds and compositions effective in controlling pathogenic microorganisms, and particularly to derivatives of methenamine.

The preferred known chemotherapeutic agents against many infections of the intestinal tract are 5-chloro-7- iodo-8-quinolinol and sulfaguanidine. The first mentioned compound is not well tolerated by persons allergic to iodine. The latter is relatively weak in its antimicrobial elfects. Methenamine, mandelic acid, and the salt of methenamine with mandelic acid have been used as disinfectants for the urinary tract.

It has now been found that quaternary ammonium salts of the formula in which R is lower alkoxy, preferably methoxy, or hydroxy, and X- is the anion of an acid at least as strong as phosphoric acid, have much stronger bacteriostatic efiects in vitro against a wide variety of microorganisms including those which are not readily controlled by tolerable doses of the known chemotherapeutic agents, and that the quaternary ammonium salts are relatively nontoxic.

Limited tests on human patients indicate that the compounds of the invention are useful in combating intestinal infections and are well tolerated in effective amounts.

The results of comparison tests between typical compounds of this invention and known chemotherapeutic agents are tabulated in Table 1.

TABLE L-DIAMETER OF INHIBITED GROWTH ZONE, MM:

Compound Microorganism A B C D Escherichia coli 12 9 14 11 Klebsiella 28 22 9 11 Pseudomonas aeruginosa 13 16 9 1 Proteus mirabilis 25 22 9 10 Proteus vulgaris 22 11 9 11 Salmonella typhi Ty 2..-. 23 22 9 9 Salm. paratyphi:

A 21 13 9 l2 17 24 9 9 25 24 9 9 Salmonella typhi murium 21 14 9 9 Shigella N0. 108 30 25 15 11 Shigella shigae No. 401 34 33 15 10 Vibrio cholerae El Tor No. 1418.. 30 28 18 11 Vibrio cholerae 669 B 40 35 17 14 Staphylococcus aureus 26 16 15 10 Staphylococcus wood 46.-- 24 22 12 9 Norm-The tested compounds are identified in the table by capital letters as follows: A=Methenamine 2-,ethoxy-5-nitrobenzyl chloride; B=Methenamine 2-hydroxy-5-nitrobenzyl chloride; C=5chloro-7-lodo- 8-quinolin0l; D=Su1faguanidine.

In testing the compounds, discs of filter paper having a diameter of 9 millimeters were sterilized in an autoclave and placed on cultures of the microorganisms on agar plates. 10% solutions or suspensions of each tested compound containing 2.5 mg. of the compound were applied to the discs, and the cultures carrying the discs were incubated at 37 C. Table 1 lists the diameters of the zones in which the compounds were elfective in inhibiting microbial growth. A diameter of 9 mm. indicates no practical bacteriostatic action, and a large diameter value is indicative of high bacteriostatic potency.

Additional comparison tests were made with methenamine and Compounds A and B of this invention. In these tests, solid nutrient mixtures (blood plates) containing 25, 50, and mg./ 100 ml. of Compounds A and B, and 100 mg./10O ml. methenamine (Compound E) were inoculated with the listed microorganisms, and the growth of the cultures after incubation at 37 C. was evaluated qualitatively. The symbols employed have the following meaning in Table 2:

- No growth of the inoculum (i) Very little growth i Weak growth Normal growth Compound B, mg./dl.

Compound A, mg./dl.

Microorganism Escherichia coli Klebsiella :1: Pseudueruginosm- Salm.typhi Ty 2/728 ,Sfiparotyphi A S.paratyphi B 223. S.paratyphi C 502. S.typhi murium Salmenleritidis Shigella No 108 Shthigae No 401-. Sh.shigae No 406-. shflerneri 102 Typ. Staphyloc. aurcus Staphyloc. Wood 46.. Vibrio cholera 1418 Vibrio cholera 38383- Vibrz'o chclera 34580- lllllllllllllllll lllllllllllllllllll llllifH-llllH-H-llll llllllllllllllllll lllllllllllllllllll EllllH' The compounds of the invention are practically nontoxic. The median lethal dosis DL in oral application to mice is above 8000 mg. per kg. It could not be determined with any precision since dosage rates higher than 8000 mg./kg. cannot be applied. No unusual side effects were observed with the large doses that were given. The value of DL in mice for 5-chloro-7-iodo-8-quinolinol (Compound C) is 7200 mg./kg. under the same conditions under which Compounds A and B were tested.

When ten rats were fed daily doses of 100 mg./ kg. of Compounds A and B for thirty days by means of an esophagus tube in addition to their normal food and water, they did not show any noticeable differences in behavior as compared to a control group of ten rats not receiving the compounds of the invention. The weight changes in both groups and the results of blood tests performed three times on each animal during the tests were normal and no significant differences could be found between the two groups. All rats were killed at the end of the test period, and their vital organs were subjected to histological examination. No pathological changes were found in the livers, lungs, spleens, thymus, kidneys, ovaries, testes, or blood vessels of the rats that had received the compounds of the invention.

Limited clinical data available at this time indicate that a dosage of 1.5 to 2 g. of the compounds of the invention is effective in adult patients suffering from enteritis and enterocolitis. No side effects have been observed when the active agents of the invention were applied in dosage units of 250 mg. in the form of drages. Two drages given three to four times a day caused rapid relief of symptoms, such as diarrhea, in most cases.

The compounds of the invention are prepared by reacting methenamine with an equimolecular amount of a 2-hydroxyor 2-alkoxy-5-nitrobenzyl ester of the formula wherein R is hydroxy or lower alkoxy, and X is the anionic radical of a physiologically tolerated acid, at least as strong as phosphoric acid. The 2-hydroxyand 2-methoxy-S-nitrobenzyl halides are most readily available and are preferred. The reaction occurs readily in a liquid medium, such as an inert solvent, at any temperature at which the reaction mixture is liquid, a reaction temperature of 20 to 50 C. being most convenient.

The several compounds of the invention can also be converted into each other by a double reaction of the type.

wherein R is hydroxy or lower alkoxy, X and X- are anions of an acid at least as strong as phosphoric acid, and Y is a cation whose salt with X is much less soluble than the desired, antimicrobial compound in any convenient solvent. The starting materials are mixed in stoichiometrically equivalent amounts, and the reaction products are then separated by filtration, decantation, centrifuging, or the like. The reaction is rapid in solvent in which the reactants ionize, but is not limited to such solvents.

The following examples further illustrate the manner of making and using the compounds of the invention.

EXAMPLE 1 9.38 g. 2-hydroxy-5-nitrobenzyl chloride (0.05 mole) of high purity were dissolved in 250 ml. chloroform, and the solution was added in a thin stream with stirring to a solution of 7.01 g. pure methenamine (0.05 mole) in ml. chloroform. A slightly exothermic reaction started at once, and yellow methenamine 2-hydroxy-5- nitrobenzyl chloride started precipitating at once. The reaction mixture was further stirred for 18 hours at ambient temperature whereupon the precipitate was filtered off with suction and dried in a vacuum at room temperature. It weighed 16.4 g. (100% yield) and melted with decomposition at C.

It was identified by elementary microanalysis and by its equivalent Weight as C H ClN O Calculated (percent): C, 47.65; N, 21.38; Cl, 10.82. Found (percent): C, 47.44; N, 21.13; Cl, 10.55.

The equivalent weight, as determined with HC1O in glacial acetic acid in the presence of mercury acetate was 329.8 as compared to a calculated value of 327.69.

Methenamine 2-hydroxy-5-nitrobenzyl chloride is only sparingly soluble in cold water and practically insoluble in the usual organic solvents. Methanol or ethanol may therefore be used instead of chloroform in the aforedescribed procedure.

EXAMPLE 2 70 g. 2-methoxy-5-nitrobenzyl chloride (0.348 mole) of high purity were dissolved in 400 ml. chloroform, and 48.7 g. pure methenamine (0.348 mole) were gradually added with stirring and dissolved almost completely. Methenamine 2-methoxy-5-nitrobenzyl chloride started precipitating after about two hours at ambient temperature, and stirring was continued for three days.

The precipitate was then recovered by suction filtration and dried in a vacuum. It weighed 102.7 g. (86.3% yield) and melted with decomposition at 184 C. The compound was identified as C H ClN O by elementary microanalysis and by its equivalent weight which was determined as in Example 1.

Calculated: Eq. wt. 341.8; C, 49.19%; N, 20.49%; Cl, 10.37%. Found: Eq. wt. 339.8; C, 49.10%; N, 20.23%; Cl, 10.24%.

The compound dissolves very readily in water and methanol, is soluble in glacial acetic acid, slightly soluble in ethanol, and only sparingly soluble in other common organic solvents.

EXAMPLE 3 Methenamine 2-methoxy-5-nitrobenzyl bromide was obtained in the same manner as in Examples 1 and 2 by reacting 8.55 g. 2-methoxy-5-nitrobenzy1 bromide with 4.87 g. methenamine in 40 ml. chloroform. The compound decomposes and melts at about 200 C. Similarly, 2-hydroxy-S-nitrobenzyl bromide yielded methenamine 2-hydroxy-S-nitrobenzyl bromide.

EXAMPLE 4 5 g. methenamine 2-methoxy-5-nitrobenzyl chloride (0.0146 mole) were reacted in 30 ml. water with 2.3 g. powdered silver sulfate (0.0073 mole). The mixture was shaken at ambient temperature for two hours. The silver chloride formed was removed by filtration, and the filtrate was evaporated to dryness in a vacuum at ambient temperature.

The residue consisted of 4.48 g. methenamine Z-methoxy-S-nitrobenzyl sulfate (86% yield) having a melting point of 90-91 C. The compound was identified by elementary microanalysis:

Calculated for C H N O S (percent): C, 47.45; N, 19.75; S, 4.53. Found (percent): C, 47.62; N, 19.49; S, 4.6.

It dissolves readily in water, methanol, and warm ethanol, but is only sparingly soluble in chloroform and lowboiling petroleum hydrocarbons.

EXAMPLE 5 g. methenamine 2-methoxy-5-nitrobenzyl chloride (0.0292 mole) and 5 g. silver nitrate (0.0292 mole) were stirred in 50 ml. water and 8.5 g. methenamine 2-methoxy- S-nitrobenzyl nitrate were recovered from the reaction mixture as described in Example 4.

The nitrate sinters at 167 C. and melts at 168 -168.5 C. It is readily soluble in water, but insoluble or only sparingly soluble in common organic solvents. It was identified by elementary microanalysis:

Calculated for C H N O (percent): C, 45.65; N, 22.82. Found (percent): C, 45.51; N, 22.56.

Salts of methenamine 2-hydroxy-5-nitrobenzyl hydroxide and of its lower alkyl ethers with all strong acids are readily prepared from methenamine and the corresponding 2-hydroxy-5-nitrobenzy1 esters or 2-lower-alkoxy-5-nitrobenzyl esters, as illustrated in Examples 1 to 3 or by double reaction of salts as illustrated in Examples 4 and 5. The salts with acids weaker than phosphoric acid are not stable enough and have not been isolated successfully.

The quaternary ammonium salts of the invention are compounded with suitable carriers, excipients, and compatible other physiologically active agents in the usual manner to convert them to dosage units, as illustrated in the following example.

6 EXAMPLE 6 2.5 kg. methenamine Z-methoxy-S-nitrobenzyl chloride were granulated with starch and gelatine as an inert excipient in the usual manner, and 100,000 tablets were formed from the granulate on a press. The tablets were coated with sugar syrup and further with a conventional enteric coating to prevent dissolution in the gastric fluid.

What is claimed is:

1. A compound of the formula References Cited UNITED STATES PATENTS 3,524,854 \8/1970 Kukn 260-2485 JOHN M. FORD, Primary Examiner us. 01. X.R. 424-249 g 3 

